FIG. 1 depicts a schematic lateral view of a road section 1 equipped with a luminaire 1 generating an asymmetrical light beam. The luminary, or candelabra, comprises a luminary post 2 and luminary head 3.
It is known to use reflectors to create asymmetrical beams output from the outdoor luminaries. Various reflector systems have been proposed to provide an asymmetrical beam. Such reflector systems are quite bulky.
For street lighting, usual light sources are high intensity discharge lamps like sodium vapor lamps, fluorescent balloons or fluorescent tubes. However, these kinds of sources are quite bulky and they require a frequent and time-consuming maintenance. A consequence of bulkiness is that the luminary heads also are bulky, which may be a drawback under windy conditions.
Other luminaries consists in using Light Emitting Diodes (LEDs) as light sources with primary lenses shaped to obtain a determinate and fixed light effect. Such types of primary lenses are disclosed for example in WO2008/122941, EP 1 621 918, US2006/138437, WO98/33007.
Led based luminaries are more and more desirable nowadays for both indoor and outdoor applications. They present several advantages over traditional technologies, amongst them lifetime and better light control notably. This triggers the need for specialized optics that can cover the entire range of applications achieved by traditional sources.
For instance, it is known from US2007/0201225 to provide an asymmetric lens for LED with an additional prism or extended portion to redirect the light so as to generate an asymmetrical beams.
Such lens presents the drawback to have a complex shape which is hard and quite expensive to produce. Moreover, this kind of lens can not be used in various applications.